Coding system used to organise and refer to unidentified catfishes, though not necessarily undescribed or distinct species, of the genus Corydoras. Works in tandem with the similar C number system. The system was invented by Ian A. M. Fuller in reference to his website ‘Corydoras World’ but is now in popular use worldwide.

Phylum of generally blue-green coloured bacteria, often confused with algae, that obtain their energy via photosynthesis and include unicellular and colonial species. Some species occur commonly in aquaria where they're normally regarded as pests.